Field of the Invention
The present invention relates to a solar cell system, and a control method thereof. More particularly, the present invention relates to a solar cell system configured for minimizing a loss of power generation and outputs of solar cells in a configuration where a plurality of solar cells is connected in parallel, and a control method thereof.
Description of Related Art
A solar cell is a photo-electric conversion device, which converts solar energy into electrical energy.
Traditionally, a monocrystalline or polycrystalline silicon solar cell is widely used as the solar cell, but the silicon solar cell requires large and expensive equipment during manufacturing and a raw material of the silicon solar cell is also expensive, thus manufacturing cost and production cost are high and there is a limit in improving efficiency of the conversion of solar energy into electrical energy, wherein a new alternative has been founded.
In the present respect, as an alternative of the silicon solar cell, an interest in a solar cell, which may be manufactured with low cost using an organic material, is increased, and a perovskite solar cell of which manufacturing cost is very low attracts large attention.
The perovskite solar cell may be manufactured of a transparent electrode, adopts various colors and designs, and has a visual advantage, that is a semitransparency characteristic, in which an external portion and an internal portion of the solar cell may be semi-transparently viewed, wherein the perovskite solar cell is advantageous in a field demanding transparency when compared to a conventional silicon solar cells or other solar cells.
The solar cell has a near infinite energy source and is environmentally friendly, unlike other energy sources, so that an importance thereof is increased as time goes by, and a utilization field thereof is broadened. Accordingly, in a vehicle business field, to meet the trend, a vehicle mounted with a system utilizing a solar cell and electrical energy output from the solar cell has been developed and released.
For example, a technology in which a solar cell module is mounted in a vehicle body (a roof panel or a sunroof/panorama roof) and a vehicle uses power generated with the solar cell has been developed.
When the solar cell is applied to the sun roof or the panorama roof, there is an advantage in that the solar cell may be utilized in various application and fields while maintaining a feeling of openness provided by the sunroof or the panorama roof.
The solar cell applied to the vehicle body may also be utilized as a power supply source of a parked vehicle, and for example, it is possible to operate a heating, ventilation, and air conditioning (HVAC) system with power generated by the solar cell while parked to decrease an internal temperature of the vehicle or perform heating, internal ventilation (parking ventilation), and the like.
The related art document about the technology, in which a solar cell is mounted in a vehicle to be used as a power supply source, includes US Patent Application Publication No. 2009-0314556, U.S. Pat. No. 6,476,315, Japanese Patent Application Laid-Open No. 2013-107554, and Japanese Patent Application Laid-Open No. 2000-180253.
US Patent Application Publication No. 2012-0096885 presents an air conditioning system using generated power of a solar cell, and an operating method thereof.
In the meantime, an operational state and an output of a solar cell may be varied according to an environmental factor, including an amount of incident light, an incident angle of light, and a component temperature in a vehicle mounted with a solar cell system, and thus there is a problem in an aspect of utilization of power output from the solar cell.
As exemplified in FIG. 1, when two or more solar cells are disposed in a vehicle, a cell characteristic of each solar cell may be different, and there is a difference in an environmental condition due to a disposition location of the solar cell in the vehicle, wherein operation voltages of the solar cells may be different from each other.
As a result, when the solar cells are connected in parallel the amount of generated power is lost.
That is, when the solar cells having different operational voltages are connected in parallel, a total voltage generated from the solar cells may converge to a voltage of the solar cell having a small voltage.
Accordingly, when the solar cells are connected in parallel and are used there may be a problem in view of energy efficiency.
Referring to the example of FIG. 1, a solar cell 1 is disposed on a roof of a vehicle and a solar cell 2 is disposed on a side surface of the vehicle, and in the present case, a difference in the amount of incident light and a voltage between the two solar cells exhibited by the disposition locations is represented in Table 1 below. As shown in FIG. 1, the bold arrows show amount of the vertical incident light which is provided in a vertical direction of the vehicle in the noon. As the solar cell 1 is disposed on a roof of a vehicle and the solar cell 2 is disposed on a side surface of the vehicle, the solar cell 1 generates larger voltages than the solar cell 2. Furthermore, the gray arrows in FIG. 1 show the amount of the inclined light which is provided in an inclined direction with respect to the vehicle in the morning/afternoon. As the solar cell 1 is disposed on a roof of a vehicle and the solar cell 2 is disposed on a side surface of the vehicle, the solar cell 2 generates larger voltages than the solar cell 1.
TABLE 1NoonMorning/AfternoonAmount ofAmount ofvertical inclinedincident lightVoltageincident lightVoltageSolar cell 1LargeLargeSmallSmallSolar cell 2SmallSmallLargeLarge
Referring to Table 1, it can be seen that the voltages of the two solar cells are different due to a difference in environmental conditions, that is, a difference in the amount of incident light according to a disposition location and time.
As a result, to solve the aforementioned problem of the loss, it is normal to configure a system which adjusts the voltages of the solar cells to be equal using a separate power converting means, and the conventional art document thereof includes Japanese Patent Application Laid-Open No. 1997-294320.
According to the conventional art, in a system in which a plurality of solar cells is connected in parallel, a system in which solar cells including different numbers of serially connected cells are connected in parallel, a system in which solar cells using the different types of solar cell are connected in parallel, or a system in which solar cells, of which disposition locations in a vehicle are different, are connected in parallel, a separate power converting device including a maximum power point tracking control (MPPT) device and a DC-DC converter is disposed at an output side of the solar cell.
In the present case, the separate power converting device are disposed at the output side of at least one of solar cell modules, and an output side of the power converting device is connected to an output side of another solar cell module to match the outputs of the solar cell modules, which are connected in parallel, using the power converting means.
Another power converting device is disposed between a connection point, at which the solar cells are connected, and a load side. Power of the solar cell is converted into power which may be supplied to the load side using the power converting means.
However, in the above solar cell system, the separate power converting device is additionally disposed at the output side of the solar cell, wherein multiple losses are generated by the power conversion, increasing a loss of the entire system.
The information disclosed in this Background of the Invention portion is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person of skilled in the art.